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/* memcmp - compare memory
Copyright (C) 2013-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library. If not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
/* Assumptions:
*
* ARMv8-a, AArch64, unaligned accesses.
*/
/* Parameters and result. */
#define src1 x0
#define src2 x1
#define limit x2
#define result w0
/* Internal variables. */
#define data1 x3
#define data1w w3
#define data1h x4
#define data2 x5
#define data2w w5
#define data2h x6
#define tmp1 x7
#define tmp2 x8
ENTRY_ALIGN (memcmp, 6)
PTR_ARG (0)
PTR_ARG (1)
SIZE_ARG (2)
subs limit, limit, 16
b.lo L(less16)
ldp data1, data1h, [src1], 16
ldp data2, data2h, [src2], 16
ccmp data1, data2, 0, ne
ccmp data1h, data2h, 0, eq
b.ne L(return64)
subs limit, limit, 16
b.ls L(last_bytes)
cmp limit, 112
b.lo L(loop16)
and tmp1, src1, 15
add limit, limit, tmp1
sub src1, src1, tmp1
sub src2, src2, tmp1
subs limit, limit, 48
/* Compare 128 up bytes using aligned access. */
.p2align 4
L(loop64):
ldp data1, data1h, [src1]
ldp data2, data2h, [src2]
cmp data1, data2
ccmp data1h, data2h, 0, eq
b.ne L(return64)
ldp data1, data1h, [src1, 16]
ldp data2, data2h, [src2, 16]
cmp data1, data2
ccmp data1h, data2h, 0, eq
b.ne L(return64)
ldp data1, data1h, [src1, 32]
ldp data2, data2h, [src2, 32]
cmp data1, data2
ccmp data1h, data2h, 0, eq
b.ne L(return64)
ldp data1, data1h, [src1, 48]
ldp data2, data2h, [src2, 48]
cmp data1, data2
ccmp data1h, data2h, 0, eq
b.ne L(return64)
subs limit, limit, 64
add src1, src1, 64
add src2, src2, 64
b.pl L(loop64)
adds limit, limit, 48
b.lo L(last_bytes)
L(loop16):
ldp data1, data1h, [src1], 16
ldp data2, data2h, [src2], 16
cmp data1, data2
ccmp data1h, data2h, 0, eq
b.ne L(return64)
subs limit, limit, 16
b.hi L(loop16)
/* Compare last 1-16 bytes using unaligned access. */
L(last_bytes):
add src1, src1, limit
add src2, src2, limit
ldp data1, data1h, [src1]
ldp data2, data2h, [src2]
/* Compare data bytes and set return value to 0, -1 or 1. */
L(return64):
cmp data1, data2
csel data1, data1, data1h, ne
csel data2, data2, data2h, ne
L(return):
#ifndef __AARCH64EB__
rev data1, data1
rev data2, data2
#endif
cmp data1, data2
cset result, ne
cneg result, result, lo
ret
.p2align 4
L(less16):
adds limit, limit, 8
b.lo L(less8) //lo:<
ldr data1, [src1]
ldr data2, [src2]
/* equal 8 optimized */
ccmp data1, data2, 0, ne
b.ne L(return)
ldr data1, [src1, limit]
ldr data2, [src2, limit]
b L(return)
.p2align 4
L(less8):
adds limit, limit, 4
b.lo L(less4)
ldr data1w, [src1]
ldr data2w, [src2]
ccmp data1w, data2w, 0, ne
b.ne L(return)
ldr data1w, [src1, limit]
ldr data2w, [src2, limit]
b L(return)
.p2align 4
L(less4):
adds limit, limit, 4
b.eq L(ret_0)
L(byte_loop):
ldrb data1w, [src1], 1
ldrb data2w, [src2], 1
subs limit, limit, 1
ccmp data1w, data2w, 0, ne /* NZCV = 0b0000. */
b.eq L(byte_loop)
sub result, data1w, data2w
ret
L(ret_0):
mov result, 0
ret
END (memcmp)
#undef bcmp
weak_alias (memcmp, bcmp)
#undef __memcmpeq
strong_alias (memcmp, __memcmpeq)
libc_hidden_builtin_def (memcmp)
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